Observations on the Py> ocystece. 18 i 
The protoplaplasm contains besides the chromatophores a number 
of larger and smaller globules lying in the polar mass and also dis¬ 
tributed along the strands ; they become intensely black under the 
influence of osmic acid and are obviously of an oily nature, they 
are shown in the “ Challenger” figures, and are well seen in figs. 1 
and 2. Lying also in the protoplasm are sometimes to be seen a 
number of clear refractive bodies of an oval shape which are 
quite unaffected by osmic acid. These bodies will be considered 
later when dealing with some of the other species of Pyrocystis in 
which they are both larger and much more numerous. 
Reproduction .—John Murray (7) in the “ Challenger ” report, 
figures a few stages in the multiplication of P. pseudonoctiluca , 
which, as far as is known, divides by simple fission. A number of 
cases were met with in my material in which the protoplasm was 
contracted away from the wall, and partially constricted into two 
balloon-shaped portions joined together by a bridge of protoplasm 
(fig. 4). At this stage I have been able to observe that nuclear 
division has already taken place, the two daughter nuclei both lying 
in the connecting bridge of protoplasm, but separated by an appre¬ 
ciable distance. In a few cases stages, were observed, as figured in 
the “ Challenger ” report, in which two small individuals are to be 
found within the parent wall. Nothing further is known as to its 
reproduction. 
Distribution .—As mentioned earlier, P. pseudonoctiluca is found 
in all tropical and sub-tropical waters; according to John Murray (7) 
wherever the temperature is over 68° or 70°F, and the specific gravity 
of the water is not lowered by the presence of coastal or river 
water. I have found it as far north as 34° 30 y N in the Atlantic in 
November when the water was at a temperature of 60"F. An 
exceptional case is that of the Bay of Funchal, where, according to 
the “ Challenger ” report it is to be found at the surface all the year 
round. The Antarctic ship “Discovery” was able to confirm its 
presence in that locality in August, 1901. 
It often occurs in considerable abundance, Schutt (8) calculates, 
from observations made during the Hensen expedition, that in the 
Florida stream as many as 50,000 are to be found in one square 
mile. 
Luminosity .—When a “ catch ” of plankton containing this species 
is placed in a vessel, they do not sink to the bottom, as does 
the rest of the “ catch,” but remain floating free near the surface 
and shine out for a few seconds as points of bluish light directly a 
